1. Field of the Invention:
The present invention relates generally to O-type sealing rings and more particularly is concerned with an elastic roll ring for socket-type connections of pipes.
2. Description of the Prior Art:
The prior art procedure used in connecting socket type connections of pipes consisted of providing an elastic sealing ring between the insertion and socket ends of a pair of pipes. The ring has a basically round profile and a circular cross section and is rolled into the socket end of one pipe when the insertion end of another pipe is inserted into the socket. With DT-OS 2,117,317, an arrangement was made known, whereby the roll ring is designed with a lip protruding beyond the circular cross sectional circumference of the ring, the lip extending in the direction of the circumference of the ring and also with a groove extending in the direction of the circumference of the ring. The groove is less than 180.degree. distant from the back surface of the lip when the ring is viewed in cross section. In this arrangement, a vertical surface opposite the back surface of the lip forms a contact surface for the socket end of a pipe while the horizontal surface, which is perpendicular to the vertical surface, forms a contact surface for the insertion end of a pipe. Also, in this arrangement, the contact surface for the end of the socket pipe formed by the lip is specifically dislocated away from the area of the ring's central vertical plane as viewed from a cross section of one side of the ring, the result being a considerable weakening of the ring's cross section. This arrangement is intended, on the one hand, to make it possible to draw the ring around the socket end to hold it there without the use of special tools. On the other hand, the groove and the entrance of the insertion end into the groove, is intended to provide an exactly defined point of attack when the two pipes are pushed toward each other, thus causing the ring to roll. However, in the case of the prior art ring, the groove and the lip are formed in such a way that when the two pipe ends are pushed together and the ring is rolled into the space between them, the areas of weakness formed by the groove and the lip are located exactly in a so-called compaction between the inner surface of the socket and the outer surface of the insertion end of the pipe, with the result that the shearing stresses thus released cannot be controlled with certainty.
Further, with DT-AS 1,236,874 the idea was introduced of providing an elastic roll ring with an indentation extending roughly on a secant plane on the cross section of the ring so as to form a sealing and support lip protruding over the circumference of the ring. This lip is brought into contact with the remaining cross section of the ring when the pipes are pushed together, thus filling out the ring to a completely circular cross section. When installed, the end of the support end or sealing lip is likewise located directly in the compaction area, such that control of the sheering stresses and an adequate seal is not assured in this case either.